Cluster systems have realized a high availability when a plurality of information processing devices (server computers, for example) are connected on a network and problems occur in any of the information processing devices by letting other information processing devices take over and carry out the process which was being carried out by the information processing device in trouble. However, because cluster systems have a redundant configuration, compared with non-cluster systems, the power consumption is inclined to increase. Therefore, techniques for reducing the power consumption of cluster systems are important, especially for reducing the power consumption in normal operation, that is, in the redundant configuration without problems occurring in the system.
The following Patent 1 Document discloses an example of the techniques for reducing the power consumption of cluster systems in normal operation. The technique disclosed in the Patent Document 1 reduces the power consumption in normal operation by putting the information processing devices in an idle state into an operation stop state for a cluster system composed of a plurality of information processing devices. In more detail, an information processing device without jobs to process is shifted into a suspending state. Then, when applications are coming up and assigned to that information processing device, job processing is carried out by resuming the information processing device.    [Patent Document 1] JP 2003-162515 A
However, there is a mutual standby type as one kind of the cluster systems. A cluster system of the mutual standby type operates the respective information processing devices as execution systems while letting them serve as standby systems for each other at the same time. More particularly, a job execution system and a job standby system are taken as one group, and the job standby system serves to take over the job when problems occur in the job execution system. Then, the information processing devices each have job execution systems and job standby systems of different groups, and monitor each other while carrying out the jobs of the execution systems. Then, if some other information processing device falls into astute of being not possible to continue the process, then the job is taken over by the job standby system of the relevant information processing device belonging to the same group of the job execution system of the other information processing device falling into the state of being not possible to continue the process. Therefore, in a cluster system of mutual standby type, there are no information processing devices in an idle state in normal operation. Hence, the technique disclosed in the aforementioned Patent Document 1 is not applicable, and thus it is necessary to reduce the power consumption in normal operation by some other method. However, at present, there have not been any effective techniques proposed therefor.